Ubuntu 15.10 (Wily Werewolf) is available for download. Like the previous version, the changes in 15.10 are mostly bug fixes, various quality improvements and updated applications.

The major changes in this release are the update to GTK 3.16 (as well as most GNOME applications to version 3.16), along with dropping the Unity overlay scrollbars for GTK3 applications in favor of GNOME's overlay scrollbars.

Unity 7 is in maintenance mode and for this release, it has received only minor enhancements and bug fixes, most of which will most probably be backported to Ubuntu 14.04 LTS.

Unity / desktop changes in Ubuntu 15.10 (Wily Werewolf)

The most important visual change in Ubuntu 15.10 is probably the replacement of Unity's overlay scrollbars for GTK3 applications with GNOME's overlay scrollbars.

According to Will Cooke, Ubuntu Desktop Manager, the main purpose of this change is "to minimize the maintenance effort", since both GNOME and Unity overlay scrollbars have the same purpose: to maximize the screen real estate.

The new GNOME overlay scrollbars are only displayed when they are needed: there's no scrollbar by default but a small scrollbar is displayed when the pointer is moved and a larger scrollbar is displayed when the user wants to interact with it:

In Ubuntu 15.10, GTK2 applications continue to use the old Unity overlay scrollbars and so does Unity Dash.

It's also worth mentioning that since the Unity overlay scrollbars caused some parts of various GTK3 applications (mostly apps using client-side decorations) to become black or transparent, this bug should no longer occur in Ubuntu 15.10.

With Ubuntu 15.10, there are also a couple of menu changes. Firstly, there's a new dconf setting to control the delay to show the menu when pressing the Alt key. And secondly, JAyatana, a package that integrates Java Swing applications with Ubuntu's global menu and HUD, is no longer enabled by default. This change was also applied to Ubuntu 15.04 recently.

You can still enable JAyatana globally or on a per-app basis - see THIS article for details.

Other Unity changes include:

dragging an app from Dash to the Desktop to create a shortcut should now work properly;

added option to enable and disable Unity low graphics mode on the fly in CCSM or via gsettings;

fixed issues with "Always on Top" windows and Dash / HUD;

improved Dash keyboard navigation (you can now use page up/down keyboard navigation in Dash - when using these keys the view scrolls the length of the visible view; category headers that are not expandable are now skipped);

It's no longer possible to shutdown the computer when the screen is locked (this fixed a security issue which allowed the user to interact with programs that were still running for about 3 seconds, according to THIS bug report) ;

various other bug fixes and small enhancements - a complete Unity changelog can be found HERE.

With this release, Image Viewer (Eye of GNOME) was redesigned and it now uses header bars however, under Unity it was patched to use a traditional titlebar and menu. There are also new controls to quickly zoom in and out and the properties sidebar has been refined:

Not all GNOME apps available by default in Ubuntu were updated to version 3.16 though. Nautilus is still at version 3.14.2 and Gedit is even older, Wily shipping with version 3.10.4.

Under the hood, Ubuntu 15.10 ships with Mesa 11.0.2, Xorg server 1.17.2, the Ubuntu Linux Kernel 4.2.0-16.19, based on the upstream 4.2.3 Linux Kernel, PulseAudio 6.0 and systemd 225. I should also mention that with this release, Ubuntu ships with BlueZ 5 (5.35).

Since the Linux Kernel version used in the previous Ubuntu release (3.19 in Ubuntu 15.04), there are quite a few changes, including a new AMDGPU kernel driver for supporting recent and near-term Radeon GPUs, Intel Broxton support, F2FS (Flash-Friendly File System) encryption support, support for Ext4 encryption, experimental support for managing clustered raid arrays, live patching the kernel code (aimed at applying security fixes without rebooting), dm-crypt CPU scalability improvements and more.